The subject of the present invention is a gate valve which comprises a body provided with a flow channel of a circular cross-section form, a cylindrical angle-transported disc gate arranged into said body and pivotable by means of a shaft means, a packing ring placed in a groove between the bottom of an expansion provided in the flow channel and the front face of a support ring extending to the flow opening, the packing ring engaging edge of the gate is a part of a circular cylinder face whose longitudinal axis is not perpendicular to the plane of the gate.
Gate valves are previously known in which the packing ring is freely placed in the valve body in a groove formed into the flow channel either perpendicularly to the flow direction or in an oblique position.
The gate valve in accordance with the invention, however, is mainly characterized in that the outer diameter of the packing ring, preferably a metallic one, is smaller than the diameter of the bottom of the packing groove and that the inner diameter of said packing ring is smaller than the width of the gate in the direction perpendicular to the pivoting-shaft but larger than, or equal to, the height of the gate at the pivoting-shaft; that is, the inside diameter of the annular ring is slightly larger than the diameter of each circular face of the cylindrical angle-transported disc gate. When the valve is being closed, the gate presses the packing ring outwards towards the bottom of the packing groove primarily in the direction of the largest diameter of the gate while, at the same time, forcing the packing to pull itself inwards tightly against the edge face of the gate primarily in the direction of the smallest diameter of the gate so that tight engagement is provided between the packing ring and gate.